You can never be 100% safe anywhere, that's a fact. BUT you can make sure you don't look like a viable target. Keeping your bag close to your body and never behind you, having it zipped up/flap closed and making sure your wallet isn't the first thing that pops out are all basic safety precautions. Thieves generally look for an easy target.
One thing I don't understand is when traveling in poor countries or places with high crime rates, you see men with their wallet peeking out of their back pocket or a fanny pack and women carrying expensive bags, huge jewelry and being careless about, generally speaking, everything. There are people that see others merely as hunting ground; to protect yourself, just make sure you don't attract their attention by being flashy and boasting a whole lotta stuff and careless behavior.
Whenever I travel alone I do my best to blend in. If not with the locals, then at least with the average tourist mass. And always carry a crossbody bag.